At least half of the world’s killer whale populations are doomed to extinction due to toxic and persistent pollution of the oceans, according to a major new study.

Although the poisonous chemicals, PCBs, have been banned for decades, they are still leaking into the seas. They become concentrated up the food chain; as a result, killer whales, the top predators, are the most contaminated animals on the planet. Worse, their fat-rich milk passes on very high doses to their newborn calves.

PCB concentrations found in killer whales can be 100 times safe levels and severely damage reproductive organs, cause cancer and damage the immune system. The new research analysed the prospects for killer whale populations over the next century and found those offshore from industrialised nations could vanish as soon as 30-50 years.

Among those most at risk are the UK’s last pod, where a recent death revealed one of the highest PCB levels ever recorded. Others off Gibraltar, Japan and Brazil and in the north-east Pacific are also in great danger. Killer whales are one of the most widespread mammals on earth but have already been lost in the North Sea, around Spain and many other places.

“It is like a killer whale apocalypse,” said Paul Jepson at the Zoological Society of London, part of the international research team behind the new study. “Even in a pristine condition they are very slow to reproduce.” Healthy killer whales take 20 years to reach peak sexual maturity and 18 months to gestate a calf.

PCBs were used around the world since the 1930s in electrical components, plastics and paints but their toxicity has been known for 50 years. They were banned by nations in the 1970s and 1980s but 80% of the 1m tonnes produced have yet to be destroyed and are still leaking into the seas from landfills and other sources.

The international Stockholm Convention on Persistent Organic Pollutants came into force in 2004 to tackle the issue, but Jepson said the clean-up is way behind schedule. “I think the Stockholm Convention is failing,” he said. “The only area where I am optimistic is the US. They alone produced 50% of all PCBs, but they have been getting PCB levels down consistently for decades. All we have done in Europe is ban them and then hope they go away.”

The researchers said PCBs are just one pollutant found in killer whales, with “a long list of additional known and as yet unmeasured contaminants present”. Further problems for killer whales include the loss of key prey species such as tuna and sharks to overfishing and also growing underwater noise pollution.

The new research, published in the journal Science, examined PCB contamination in 351 killer whales, the largest analysis yet. The scientists then took existing data on how PCBs affect calf survival and immune systems in whales and used this to model how populations will fare in the future. “Populations of Japan, Brazil, Northeast Pacific, Strait of Gibraltar, and the United Kingdom are all tending toward complete collapse,” they concluded.

Lucy Babey, deputy director at conservation group Orca, said: “Our abysmal failures to control chemical pollution ending up in our oceans has caused a killer whale catastrophe on an epic scale. It is essential that requirements to dispose safely of PCBs under the Stockholm Convention are made legally binding at the next meeting in May 2019 to help stop this scandal.” Scientists have previously found “extraordinary” levels of toxic pollution even in the 10km-deep Mariana trench in the Pacific Ocean.

“This new study is a global red alert on the state of our oceans,” said Jennifer Lonsdale, chair of the Wildlife and Countryside Link’s whales group. “If the UK government wants its [proposed] Environment Act to be world-leading, it must set ambitious targets on PCB disposal and protect against further chemical pollution of our waters.”

The research shows that killer whale populations in the high north, off Norway, Iceland, Canada and the Faroes, are far less contaminated due to their distance from major PCB sources. ”The only thing that gives me hope about killer whales in the longer term is, yes, we are going to lose populations all over the industrialised areas, but there are populations that are doing reasonably well in the Arctic,” said Jepson.

If a global clean-up, which would take decades, can be achieved, these populations could eventually repopulate empty regions, he said, noting that killer whales are very intelligent, have strong family bonds and hunt in packs. “It is an incredibly adaptive species – they have been able to [live] from the Arctic to the Antarctic and everywhere in between.”

He praised the billion-dollar “superfund” clean-ups in the US, such as in the Hudson River and Puget Sound, where the polluter has paid most of the costs: “The US is going way beyond the Stockholm Convention because they know how toxic PCBs are.”

When the crew on board Will Mure’s fishing boat Diana spot the fin of a killer whale, it’s not a photo opportunity.

It’s a day ruined.

Killer whales or orcas are adept at pinching fish off long lines, leaving fishermen out of pocket.

Mures Tasmania director Will Mure said the whales had been taking fish off his and his late father George’s lines for the past 40 years.

“They will at times take all of your catch, and sometimes that will be in excess of a tonne of fish,” he said.

“So you’ll have a pod of killer whales of maybe half a dozen that will just take the whole lot, so it is devastating.

“They essentially dive down the line we’re hauling off the bottom … and all you end up with is a bit of the lips of the fish and that’s it.”

He said orcas were extremely clever.

“They can recognise the individual noises of the boat,” he said.

“They’ll come directly to our boat and there will be other boats around and they’ll leave them alone, so they’re very smart animals.”

He said the killer whales were fussy about which fish they would take.

“When we go for blue eye — which we have traditionally always caught for the last 30-40 years — that’s where they appear and they love blue eye.”

Blue eye is a high-value fish.

“If they’re taking a tonne of fish, you’re talking in excess of $10,000 of product that they take in a day and the crew get paid as a percentage of the catch, so they’re obviously very unhappy with it as well because they don’t get any pay either,” Mr Mure said.

“They also love tuna. There was a very good tuna fishery in Tasmania some time ago, but they were so persistent with the tuna fishermen that eventually that fishery has actually moved to other parts of Australia now.”

Trying to outmanoeuvre the orcas

When the Diana returns to Tasmanian waters later this year to catch blue eye, Mr Mure has a trick up his sleeve to outsmart the animals.

“It’s not actually a new method. I don’t know why we haven’t thought about it before but there’s a hydrophone product which is actually a listening device,” he said.

“You put it into the water and you actually hear if the killer whales are in the vicinity. We’re in the process of purchasing one of those.”

But he said it was not a silver bullet.

“So we’ll hear them, and say ‘right, we can’t fish here today’, and spend a day steaming to the fish somewhere else.”

Ben Sellers, a PhD student with the Institute of Marine and Antarctic Studies, is looking at the diet and range of killer whales in Australian waters, using biochemical techniques and satellite tagging.

He has spent some time on board the Diana, and observed killer whales taking fish off long lines.

“They’ll miraculously appear just as the lines are being hauled. They are very clever animals.”

Mr Sellers said using a listening device and moving away from the orcas was a good way for the fishing industry to deal with the problem, as it breaks the cycle of animals connecting the fishing boats with a free feed.

“The more they move away from the animals, or stop the animals depredating just by changing fishing grounds, the less association there is, and the less conditioning there will be for the whales to associate boats with fish.”

He said a lot of work had been done trying to come up with an underwater acoustic deterrent, which emits sounds the killer whales want to avoid.

“They’re making developments for the North Pacific fisheries where depredation is a real issue, where killer whales take the halibut from fishermen around Alaska.

“In the Southern Ocean with the Patagonian toothfish fishery, the French have a real problem there with the killer whales, and you have actual pods specialising in taking the fish off the boats,” Mr Sellers said.

He said so far, acoustic deterrents had not worked.

That means, for now, a listening device and avoiding fishing grounds where the killer whales are waiting for a free feed, is the best bet for fishermen wanting to keep their catch.

In a scene resembling a David Attenborough documentary, tourists and crew returning from a diving expedition near South West Rocks on Saturday morning spotted six killer whales harassing two humpbacks and their calf.

The group was on its way back from exploring Fish Rock Cave, about 1.5km off Smoky Cape, when skipper of the vessel Steve Skinner noticed a splash in the water not far from the lighthouse.

Upon motoring over for a closer look, it became clear the disturbance was an orca’s dorsal fin breaking the surface, one of six in pursuit of the humpbacks.

Mr Skinner says the adult humpbacks were swimming either side of the calf in an effort to protect it from the encroaching predators.

“This is the first time in eight years at South West Rocks Dive Centre that I’ve seen killer whales,” he said.

After being distracted by the boat and playing in the bow wave briefly, the orcas’ attention reverted to making a meal of the calf.

Killer whales, or orcas, are fast, fearsome predators, but comparatively little is known about the species.

Earlier this month a rare recording of the vocalisations of killer whales was recorded off the east coast of Tasmania.

“To date there are very, very few recordings of killer whale vocalisations across Australia, certainly fewer than 20 recordings,” said David Donnelley, coordinator of Killer Whales Australia.

Researchers had dropped a camera over the side of a boat at Eaglehawk Neck to record video of a pod, when the microphone picked up the vocalisations.

“Very, very difficult to know what they were talking about. The meaning of the calls or the noises that you heard on that recording will almost be uninterpretable because we know so little about the communication of killer whales in Australian waters,” Mr Donnelley said.

“We really don’t know why they do or don’t call in a lot of cases, why they may call a little bit or infrequently is a mystery to everybody, including the acousticians.

“Killer whales are listed on the International Union for the Conservation of Nature (IUCN) Red List as ‘data deficient’ so we have no idea how many there are worldwide, or even their population at the moment,” he said.

Where killer whales travel and what they eat matters, because as an ‘apex predator’, one at the top of the food chain, they can have a strong influence on marine system and biodiversity.

“If we can be informed as to what they are eating, we can look at conflict issues, so if we eat the same things they eat, those sorts of things, plus it gives us an idea of where they go,” he said.

He said killer whales “pinch fish from fishing boats’ long lines”.

“They tend to take blue eye fish, they’re an expensive, oily fish we like to eat, and killer whales like to eat them too.

“They’re quite selective, they’ll leave fish like ling on the line, but they’ll take blue eye off, so it’s really interesting that they can tell the difference between high quality fish and low quality fish.

“And they’re really careful too, they pull the fish of real gently, they don’t hit the gear or anything like that.

“[Killer whales] are hard to see, they’re free-ranging marine mammals and so they spend 90 per cent of their time under water and they also don’t take prey on the surface very much, so any interactions you’re likely to see are very rare so they’ll take prey mostly underwater, fish, other marine mammals and they’re quite elusive.”

Citizen scientists taking photos of killer whales around Australia are helping with Mr Sellers’ research, as images of fins are compared in a database to help identify individual whales.

Mr Sellers takes biopsy samples of the known whales to study their diets.

“Specifically I use a chemical technique called signature fatty acid analysis where we take small biopsies from killer whales and we look at the percentage of fatty acids in the tissue and it tells us what they’ve been eating over a period of time,” he said.

The not-for-profit group Killer Whales Australia helped track a pod down the east coast of Tasmania, until Mr Sellers could locate them by boat off Eaglehawk Neck.

“In this instance we just got photo IDs and what we aim to do is biopsy the animals. There was a calf in this pod, so we wouldn’t biopsy, if there’s no calves present, then we will look at deploying a dart and taking a small tissue biopsy from the animal and then analysing that, matching it to a fin ID in the catalogue and then we have an idea of what that animal eats,” he said.

Mr Sellers aims use satellite tagging this summer and get more samples from killer whales in Western Australia, as well as examine French sub-Antarctic samples before completing his PhD.

“So we will probably write up two or three research papers on their diet and range, and from that work with fisheries too and advise them about what we’ve found,” he said.

Earlier this month a rare audio recording of killer whales in the wild was captured off Tasmania’s south east, and Mr Sellers said despite years of studying the species it was the first time he had heard it.

GROUNDBREAKING WA research is shedding new light on killer whales, with more than 100 individuals now identified in an orca hot-spot off Bremer Bay.

The pods, or family groups, are led by grandmother killer whales that have gone through menopause and can live for more than 100 years.

From January to April, the marine mammals frequent the Bremer sub-basin, a series of underwater canyons spanning more than 11,000sq km off the State’s south coast with water depths from 10m to 4.5km.

But where they come from and where they go after summer remains a mystery, as does the population number and much of the orcas’ mating and feeding habits.

At the forefront of research to learn more about the elusive and highly social WA killer whales is Bec Wellard, who has spent four seasons on a research boat 50km out to sea as she completes a PhD through Curtin University’s Centre for Marine Science and Technology.

She has spearheaded a “citizen science” program, using photographs of the animals’ unique dorsal fin, eye patch and saddle patch markings that has now identified more than 100 individual animals.

“The dorsal fin is as unique as a human fingerprint, with each animal having different curvatures, nicks and notches,” she said.

Known as Project Orca, her work has contributed to a catalogue of killer whales published this week.

The animals have names including El Notcho, named for a deep notch in the dorsal fin; Holey, an animal with a hole punched neatly in the dorsal fin; and Lucky, who is missing almost the entire dorsal fin, possibly from propeller damage or entanglement.

So far there has been no successful satellite tagging program of WA killer whales, and Project Orca works uses only non-invasive techniques, including photo identification.

The south coast killer whales are an entirely seperate population from orcas at Exmouth and on the east coast.

“They’re only here from January to April, and we don’t know where they come from and we still don’t know where they go,” Ms Wellard said.

She said the species was “matrilineal, which means the female rules the roost”.

“They have a culture, they have their own language and dialects and they pass that on to the younger generation,” she said.

Orcas are thought to congregate in the Bremer sub-basin because it is a feeding hot-spot, thanks to deep ocean upwelling.